1. Field of the Invention
The present invention relates to an image processing apparatus having OSD (on-screen display) function, and more particularly to an image processing apparatus for transmitting RGB color signals among the OSD signals for displaying the explanation about the guidance for specific functions or the operational status thereof on the screen through one line.
2. Prior Art
An image processing apparatus such as a television has an OSD (on-screen display) function for displaying the operational status thereof. Such an image processing apparatus having OSD function displays the operational statuses for the control of volume, selection of channel, change of mode, or PIP (picture in picture) function on the screen when a user operates remote controller or various operating buttons.
FIG. 1 is a block diagram for a general image processing apparatus having OSD function. The image processing apparatus has a microprocessor 10 for generating OSD signals according to the control signal Cin inputted by the operation of a remote controller or the like, a signal processor 17 for synthesizing the OSD signals transmitted from the microprocessor 10 with image signals Vin, and image output part 19 for outputting the signals processed by the signal processor 17 toward an image display device (not shown) such as a CRT (Cathode-Ray Tube) or the like.
The microprocessor 10 contains an OSD signal generator 11 and a matrix circuit 12. The OSD signal generator 11 generates the OSD signals according to the inputted control signal Cin. The matrix circuit 12 receives the signals from the OSD signal generator 11, and produces blanking signals Y and RGS color signals which consist of red color signal R, green color signal G, and blue color signal B. Each color signal of the RGB color signals is transmitted with lines allotted respectively thereto, and the blanking signals Y are transmitted through at least one line. The OSD signals produced by the matrix circuit 12 are inputted to the signal processor 17.
The signal processor 17 comprises an OSD signal processor 15 and an image signal processor 16. The OSD signals inputted to the signal processor 17 are changed by the OSD signal processor 15 into OSD character signals which consist of R, G, B, and Y character signals. The OSD character signals are inputted to the image signal processor 16, and the image signal processor 16 synthesizes the image signals Vin with the OSD character signals. The synthesized signals are inputted to the image output part 19, and the image output part 19 changes these signals into signals Vout for displaying on the CRT. The OSD characters are displayed by the signals vout, and then the user perceives the statuses of the channel selection, volume control, etc., through the OSD characters displayed on the screen.
However, in such an image processing apparatus, for the transmission of the RGB color signals R, G, B and the blanking signals Y which are inputted from the microprocessor 10 to the OSD signal processor 15, at least four ports in the microprocessor 10 should be occupied. Thus, the layout for the processing of the OSD signals between the microprocessor 10 and the OSD signal processor are complex. Furthermore, due to a recent tendency to allot additional port for use in the luminance control in order to control the brightness of the OSD character, the layout of the microprocessor becomes more complex. Moreover, when the RGB color signals R, G, B and the blanking signals Y are transmitted, the interference between each of the signals may occur to generate noise, so the OSD characters are displayed in an unstable fashion on the image display device.
Further, the color of the OSD character is determined merely by the ON/OFF control of the RGB color signals R, G, B, so only about eight colors can be implemented and diverse colors cannot be provided.